Thermographic copying machine with a series of driven rollers to separate the copy and transfer sheets



June 6, 1967 B. RUSSELL ET AL 3,324,292

THERMOGRAPHIC YING MACHINE W A SERIES 0 RIVEN TO SEP FER ROLLERS ABATE COPY NS 5 TS Filed t. 26, 196

FIG!

lA/VENTORS ROBERT B. RUSSELL GERARD A. VITU BY,

ATTORNEYS United States Patent 3,324,292 THERMUGRAPHIC COPYING MACHINE WITH A SERIES OF DRIVEN ROLLERS T0 SEPARATE THE COPY AND TRANSFER SHEETS Robert B. Russell, Newton, Mass, and Gerard A. Vitu, Evanston, IlL, assignors, by mesne assignments, to Robert B. Russell, Boston, Mass.

Filed Oct. 26, 1964, Ser. No. 406,318 3 Claims. (Cl. 250-65) This invention is an improved thermographic copying machine adapted for radiant energy induced copying by front printing and to operate with a continuous transfer sheet contained within the machine. More specifically, this invention is concerned With such a copying machine that is particularly designed to operate with precut copy sheets individually inserted into the machine along with the indicia-bearing original.

US. Patent No'. 3,048,695, in the name of one of the present inventors, illustrates the type of thermographic copying machine with which this invention is concerned. This patent develops the principals upon which the thermographic copying machine operates and it will not be necessary to re-describ'e in great detail the basic elements of the machine. Succinctly, the machine operates by placing first the indicia-bearing original against a print roll over which is placed the copy sheet. Both sheets are held firmly against the print roll by .a transfer sheet which contains the transfer or imaging material such as a dyed wax on its surface. The three superimposed sheets are then passed under a high intensity radiant energy source such as a lamp which causes the imaging material to soften or melt in the areas corresponding to the images on the original andto transfer to the copy sheet. The three sheets are thereafter separated with the continuous trans fer sheet being passed to a take-up roll within the machine.

The thermographic copying machine of US. Patent No. 3,048,695 was designed to operate with a continuous copy sheet contained within the machine with only the indiciabearing original being required to be inserted into the machine. The copy sheet, after having been imaged at the printing station, passed out of the machine and individual copies were obtained by tearing or cutting the imaged sheet as required. The use of a continuous copy sheet is not a wholly satisfactory type of operation. In

many of the applications for thermographic copying it is' desirable to operate with individual precut copy sheets.

The imaging material carried by the transfer sheet is usually a pigmented or dyed thermoplastic material such as a wax having a select melting point. Imaging is accomplished by causing the wax to melt in the imaged area by the application of the radiant energy while the copy sheet is held firmly against the wax surface. The molten wax in the imaged areas is transferred to and to some extent absorbed by the copy sheet and the wax is thereafter partially or completely solidified. The copy sheet is then separated from the transfer sheet and rejected from the machine. It has been found, however, that the copy sheet tends to adhere rather firmly to the transfer sheet and that with an improperly designed machine, the machine will quite often eat the copy when precut copy sheets are used. This invention is directed to this particular problem.

In addition, it has been found to be important to so design the machine that the greatest amount of tension guided to the exit slot.

3 ,324,292 Patented June 6, 1967 possible is exerted on the transfer sheet on the print roll at the time it is being exposed. This assures that the transfer sheet is firmly pressed against the copy sheet and the copy sheet is firmly pressed again-st the original. This minimizes any air gaps between the sheets, prevents relative motion of the sheets and permits ready transfer of the imaging medium from the transfer sheet to the copy sheet. The present copy machine is sodesigned as to maximize the tension on the transfer sheet while it is passing through the printing station.

The conditions existing at the time the copy sheet is being separated from the transfer sheet influence the quality of the copy produced. If the copy sheet is not taut at the time of separation and the separation is not firm and clean and on a constant line, then variations in image density may occur because the imaging material is usually quite soft at the time of separation. In a preferred embodiment, the copying machine of this invention has means for tensioning the copy sheet as it separates from the transfer sheet and for positively ejecting the copy sheet and the original from the machine.

In the present invention the transfer sheet, copy sheet and the original after having been passed around the print roll past the printing station are separated abruptly from contact with the copy sheet, positively ejects the copy sheet from the machine and assures its the transfer sheet.

The roller edge consists of a rigid bar carrying a series of rollers the outer surfaces of which consist of a resilient material of low heat capacity and conductance to avoid heat build-up at this point. The rollers prevent the tension applied to the transfer sheet from being lost at this point to friction so that the transfer sheet has the maximum amount of tension applied to it at the printing station. The rollers are preferably positively driven as a further improvement.

The take-off roll is a soft resilient roll pressing against the print roll just beyond the roller edge. The separated copy and original are directed into the nip formed by the take-off roll and the print roll are thereby positively The take-olf roll is driven at preferably a slightly greater rate of speed than the print roll and yieldingly engages the copy sheet as it enters the nip with the result that the copy sheet is pulled taut and remains so until fully separated from the transfer sheet. This feature materially improves the quality of the copy produced and the reliability of the machine.

In brief compass, the present invention is a thennographic copying machine designed to operate with a continuous internally supplied transfer sheet and to handle precut copy sheets. It comprises, in combination, a housclean separation from ing having mounted therein a transfer sheet supply roll,

roll. An elongated roller edge closely adjacent and parallel to the axis of the print roll presses against the transfer sheet at a point beyond the printing station and the transfer sheet is caused to undergo bending as it passes over the roller edge which causes the unprinted leading edge of the copy sheet to separate from the transfer sheet. The transfer sheet is maintained under tension as it passes from the supply roll to the take-up roll and little or none of this tension is lost at the point of separation. A soft take-off roll contacts the print roll beyond but closely adjacent to the roller edge, forming a nip with the print roll. The separated leading edge of the copy sheet contacts the take-off roll and is positively guided into the nip. The take-off roll is preferably driven at a slightly greater circumferential speed than that of the print roll and is positioned to yieldingly or slidingly engage the copy sheet in the nip with the result that the copy sheet is first snapped taut and then maintained taut until fully separated from the transfer sheet. This crisp separation optimizes the amount of imaging material transferred to the copy sheet, and the uniformity of the transfer.

FIG. 1 is a schematic illustration showing the general arrangement of the components of a thermographic copying machine based on the principles of this invention in side elevation with the housing being in part broken away to expose the interior elements;

FIG. 2 illustrates the roller edge in enlarged detail; and

FIG. 3 shows in enlarged cross-section the relative positions of the roller edge, the print roll and the take-off roll, and illustrates the separating action that occurs.

In FIG. 1 two portions of the housing of the machine are indicated by and 11 which portions are hinged at 12 to permit portion 10 to be pivoted up and away from portion 11 to expose the transfer sheet and permit it to be threaded-up. The transfer sheet supply roll is indicated at 13, the print roll at 16 and the transfer sheet take-up roll at 21. The transfer sheet 14 passes from the supply roll 13 over an idler roll 15 which firmly presses it against the print roll 16. The transfer sheet then follows the surface of the print roll 16 beyond the radiant energy source 17 to the roller edge, generally indicated at 18. Roller edge 18 is an elongated rigid bar (see FIG. 2) having mounted on the edge pressing against the transfer sheet a series of felt covered rollers 18a having a diameter of preferably less than 0.25". The rollers 18a are mounted on a common shaft and are driven at a circumferential speed equal to or slightly greater than the lineal speed of the transfer sheet by gear 18b which interconnects with the drive of the machine in a conventional manner (not shown). After separation of the copy sheet, the transfer sheet passes over guide roll 20 to the take-up roll 21. Take-up roll 21 is driven through a slip-clutch arrangement and supply roll 13 and/or roll 15 are retarded or dampened so that transfer sheet 14 is fully and smoothly tensioned over the print roll.

A take-off roll 19 with a soft rubber surface 19a (see FIG. 3) presses against the print roll below the roller edge and forms a nip therewith. Roll 19 may be driven by drive means not shown to cause roll 19 to rotate preferably at a slightly greater surface velocity than that of the transfer sheet.

In operation, the machine is turned on and the transfer sheet moves and the rolls rotate in the directions indicated by the direction arrows. The copy sheet 31, superimposed on the original 30 on the indicia-bearing side, is introduced into the machine as indicated by direction arrow 22 through a suitable slot and enters the nip formed by rolls 15 and 16. The three copying elements, i.e., the transfer sheet, copy and' original, are then carried past the light source 17 to the roller edge 18. At this point the transfer sheet is bent away from the print roll 16 and the leading edge of the copy sheet separates therefrom. As shown in FIG. 3 the copy sheet 31 tends to follow the transfer sheet somewhat, but the spacing of take-off roll 19 is such that when the leading edge of a copy sheet contacts the soft surface of the take-off roll 19 it is directed into the nip without difficulty. In the absence of the take-off roll, depending on the material being copied, the copy sheet could follow the transfer sheet to the extent of falling into the machine. If the surface of roll 19 is hard and smooth, the copy may tend to buckle when its leading edge contacts the roll.

The copy sheet and the original after entering the nip formed by take-off roll 19 and print roll 16 and are then positively ejected from the machine as indicated by direction arrow 23 with the copy sheet, under the urging of the slightly faster moving take-01f roll, being pulled taut until free of the transfer sheet. An elongated guide platform 24 may be used to assist the travel of the papers from the machine.

It has been found that if the surfaces of rollers are of metal or other material having a fairly good heat conductance and capacity to store heat, the heat brought to the rollers by the transfer sheet will be picked up by the rollers and the pattern of the rollers will appear on the copy sheet as a result of the increased temperature of the rollers softening the thermoplastic imaging medium.

The transfer sheet is preferably quite thin and flexible enough in relation to tension applied to it to readily conform to the contour of the roller edge and pass smoothly over it. The copy sheets, on the other hand, are preferably relatively stiff and non-stretchy so as to resist being bent around the roller edge. It is usually preferable not to image the copy sheets right up to the leading edge as this may cause the leading edge to follow the transfer sheet around the roller edge. In some cases copy paper hvaing a leading edge not susceptible to imaging can be used.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims:

1. A thermographic copying apparatus adapted to handle cut copy sheets comprising, in combination; a housing having mounted therein a transfer sheet supply roll; a transfer sheet take-up roll; a print roll intermediate said transfer sheet supply and take-up rolls; an infrared radiation energy source defining between it and said print roll a printing station; drive means adapted to cause a continuous transfer sheet to pass under tension from said transfer sheet supply roll to said transfer sheet take-up roll with the side bearing the transfer medium facing said print roll; a roller edge between said printing station and said transfer sheet take-up roll and placed transverse to said transfer sheet and adjacent said print roll, said roller edge consisting of an elongated bar the edge of which contacting said transfer sheet contains a series of rollers, means for positively driving said rollers in the direction of travel of said transfer sheet; a take-off roll with a resilient surface beyond and closely adjacent to said roller edge forming a nip with said print roll and adapted to yieldingly engage copy sheets issuing past said roller edge; means for supplying a cut indicia-bearing original with a superposed cut copy sheet to said printing station between said transfer sheet and said print roll with said indicia-bearing original bearing directly against said print roll with the indicia thereof facing said transfer sheet; and means adapted to remove said indicia-bearing original and said copy sheet when separated from said transfer sheet from said housing; said transfer sheet supply and take-up rolls and said roller edge being so positioned that said transfer sheet passes tightly over a portion of the circumference of said print roll at said printing station and then over said roller edge whereby said copy sheet separates from said transfer sheet and enters said mp.

2. In a thermographic copying machine wherein a mov* ing transfer sheet within the machine is placed adjacent to a copy sheet, and heat activatable, indicia-forming material is transferred from said transfer sheet to said copy sheet, means for continuously separating said transfer sheet from said copy sheet comprising, a separating edge comprising a series of small rollers, means for positively driving said small rollers in the direction of travel of said transfer sheet, means for tensioning said transfer sheet over said separating edge, said separating edge together with said tensioning means causing said transfer sheet to bend away from said copy sheet, and means closely adjacent said separating edge for engaging and drawing said copy sheet away from said separating edge.

3. The machine of claim 2 wherein the outer surface of said small rollers are of a resilient material of low heat capacity and conductance.

References Cited UNITED STATES PATENTS RALPH G. NILSON, Primary Examiner. W, F. LINDQUIST, Assistant Examiner. 

1. A THERMOGRAPHIC COPYING APPARATUS ADAPTED TO HANDLE CUT COPY SHEETS COMPRISING, IN COMBINATION; A HOUSING HAVING MOUNTED THEREIN A TRANSFER SHEET SUPPLY ROLL; A TRANSFER SHEET TAKE-UP ROLL; A PRINT ROLL INTERMEDIATE SAID TRANSFER SHEET SUPPLY AND TAKE-UP ROLLS; AN INFRARED RADIATION ENERGY SOURCE DEFINING BETWEEN IT AND SAID PRINT ROLL A PRINTING STATION; DRIVE MEANS ADAPTED TO CAUSE A CONTINUOUS TRANSFER SHEET TO PASS UNDER TENSION FROM SAID TRANSFER SHEET SUPPLY ROLL TO SAID TRANSFER SHEET TAKE-UP ROLL WITH THE SIDE BEARING THE TRANSFER MEDIUM FACING SAID PRINT ROLL; A ROLLER EDGE BETWEEN SAID PRINTING STATION AND SAID TRANSFER SHEET TAKE-UP ROLL AND PLACED TRANSVERSE TO SAID TRANSFER SHEET AND ADJACENT SAID PRINT ROLL, SAID ROLLER EDGE CONSISTING OF AN ELONGATED BAR THE EDGE OF WHICH CONTACTING SAID TRANSFER SHEET CONTAINS A SERIES OF ROLLERS, MEANS FOR POSITIVELY DRIVING SAID ROLLERS IN THE DIRECTION OF TRAVEL OF SAID TRANSFER SHEET; A TAKE-OFF ROLL WITH A RESILIENT SURFACE BEYOND AND CLOSELY ADJACENT TO SAID ROLLER EDGE FORMING A NIP WITH SAID PRINT ROLL AND ADAPTED TO YIELDINGLY ENGAGE COPY SHEETS ISSUING PAST SAID ROLLER EDGE; MEANS FOR SUPPLYING A CUT INDICIA-BEARING ORIGINAL WITH A SUPERPOSED CUT COPY SHEET TO SAID PRINTING STATION BETWEEN SAID TRANSFER SHEET AND SAID PRINT ROLL WITH SAID INDICIA-BEARING ORIGINAL BEARING DIRECTLY AGAINST SAID PRINT ROLL WITH THE INDICIA THEREOF FACING SAID TRANSFER SHEET; AND MEANS ADAPTED TO REMOVE SAID INDICIA-BEARING ORIGINAL AND SAID COPY SHEET WHEN SEPARATED FROM SAID TRANSFER SHEET FROM SAID HOUSING; SAID TRANSFER SHEET SUPPLY AND TAKE-UP ROLLS AND SAID ROLLER EDGE BEING SO POSITIONED THAT SAID TRANSFER SHEET PASSES TIGHTLY OVER A PORTION OF THE CIRCUMFERENCE OF SAID PRINT ROLL AT SAID PRINTING STATION AND THEN OVER SAID ROLLER EDGE WHEREBY SAID COPY SHEET SEPARATES FROM SAID TRANSFER SHEET AND ENTERS SAID NIP. 